Gas turbine stationary blade

ABSTRACT

The gas turbine stationary blade comprises a stationary blade section provided therein with a passage for cooling air, an inner shroud for supporting the stationary blade section on the side of a discharge port of the cooling air, and a plurality of segments each of which includes at least one stationary blade section and at least one inner shroud. A low passage is pulled out from the discharge port of the cooling air, and the flow passage is introduced to a front edge corner section of the inner shroud and is extended rearward along a side edge of the inner shroud.

FIELD OF THE INVENTION

The present invention relates to a cooling structure of a gas turbinestationary blade mainly used for a two or more-staged stationary blade.

BACKGROUND OF THE INVENTION

A stationary blade of a gas turbine used for generating electric powerprovides a flow passage for combustion gas, of which temperature reachesabout 1300° C. Therefore, in order to prevent melt or damage of thestationary blade by combustion gas, various cooling structures areprovided to the gas turbine stationary blade. As a technique concerningsuch a cooling structure, there is a widely-known technique in which apassage for cooling air is provided in the gas turbine stationary blade,cooling air is sent into this passage, thereby cooling the gas turbinestationary blade from inside (refer to Japanese Patent ApplicationLaid-open No. 11-132005 for example).

The gas turbine stationary blade has a dividable structure capable ofassembling and disassembling the gas turbine stationary blade inconsideration of easy maintenance after installation thereof. FIG. 14 isa perspective view showing a segment 1 that is a unit constituentelement of a two-staged stationary blade of a gas turbine. Each unitconstituting this segment 1 comprises a substantially parallelograminner shroud 2, one columnar stationary blade section 3 whose one end isfixed to the inner shroud 2, and a substantially parallelogram outershroud 4 installed substantially in parallel to the inner shroud 2 andfixed to the other end of the stationary blade section 3. The segment 1comprises a pair of the units welded and connected to each otherside-by-side. The gas turbine stationary blade comprises a plurality ofsegments 1 connected to one other side-by-side through detachableconnection members (not illustrated) such as bolts such that the gasturbine stationary blade is formed into an annular structure as a whole.The gas turbine stationary blade is fixed and installed in a gas turbinecasing (not illustrated) with a cantilever structure by means of legs 5provided on an outer peripheral side face of the outer shroud 4.

A bolt joint section 7 of the segment 1 keeps a specific distance so asto absorb expansion of the gas turbine stationary blade when the gasturbine is driven. This distance is set such that the distance is madezero by expansion of the gas turbine stationary blade when the gasturbine is driven. However, due to tolerance during the actual producingprocedure, a gap 7 a ranging from about 0.5 mm to 1 mm is produced inthe bolt joint section 7.

FIG. 15 is an enlarged perspective view around the inner shroud 2 shownin FIG. 14. FIG. 16 is a plan sectional view of the inner shroud 2 shownin FIG. 15. FIG. 17 is a side sectional view of the inner shroud 2 takenalong the line I—I in FIG. 16. FIG. 18 is a side sectional view of theinner shroud 2 taken along the line II—II in FIG. 16. In FIG. 15 to FIG.18, the gas turbine stationary blade has a stationary blade sectionfront edge passage 9 and a stationary blade section rear edge passage 10isolated from each other by a rib 8 which are provided inside thestationary blade section 3. The stationary blade section front edgepassage 9 is in communication with an open chamber 11 provided in theinner shroud 2. The stationary blade section rear edge passage 10 passesthrough the inner shroud 2, and is in communication with a cavity 12formed in a bottom face section of the inner shroud 2. The open chamber11 and the cavity 12 are isolated from each other by a bottom plate 13installed on the bottom face section of the inner shroud 2. A member 14,shown in FIG. 17, in the stationary blade section 3 is an impingementtube 14 comprising a metal member inserted into the stationary bladesection front edge passage 9 and the stationary blade section rear edgepassage 10 so as to subject the stationary blade section 3 toimpingement cooling.

In the inner shroud 2, a front edge 15 is located in upstream portion inthe flow passage for combustion gas 6. A front edge flow passage 16 isprovided along the front edge 15. The front edge flow passage 16 and theopen chamber 11 are in communication with each other through anintermediate flow passage 17 provided therebetween. A regulating plate18 is laid on a floor section of the front edge flow passage 16 tonarrow a cross sectional area of the flow passage. A plurality ofturbulators 20 are provided on the regulating plate 18 and a ceilingsection of the front edge flow passage 16 to agitate the cooling air 19.

From an outlet orifice of the front edge flow passage 16, a central flowpassage 21 having a cross sectional area smaller than that of the frontedge flow passage 16 is pulled out. The central flow passage 21 comesout from a rear edge 23 of the inner shroud 2 that is downstream of theflow passage of combustion gas along the welded joints 22 of the innershrouds 2. From a position near an inlet orifice of the front edge flowpassage 16 also, a side edge flow passage 24 having a cross sectionalarea smaller than that of the front edge flow passage 16 is pulled out.The side edge flow passage 24 comes out from the rear edge 23 along aside edge 25 of the inner shroud 2 (refer to FIG. 16 and FIG. 18). Thecooling structure is provided for each pair of units constituting thesegment 1, and a pair of left and right cooling structures are providedto constitute a cooling structure of the inner shroud 2.

At the time of actuation of the gas turbine, when the inner shroud 2 isto be cooled, cooling air 19 is sent to the impingement tube 14 in thestationary blade section 3 from the outer shroud 4. The cooling air 19subjects the stationary blade section 3 to impingement cooling, aportion of the cooling air 19 flows into the open chamber 11 in theinner shroud 2 through the front edge passage 9 of the stationary bladesection, and a portion of the cooling air 19 penetrates the inner shroud2 through the stationary blade section rear edge passage 10 and issupplied to the cavity 12 (refer to FIG. 17). The cooling air 19 whichhas flowed into the open chamber 11 flows into the front edge flowpassage 16 through the intermediate flow passage 17 to convection-coolsthe front edge of the inner shroud 2. A portion of the air flows intothe side edge flow passage 24 from an inlet orifice of the front edgeflow passage 16, convection-cools the side edge 25 of the inner shroud2, and is discharged from the rear edge 23. Remaining cooling air 19flows into the central flow passage 21 from the outlet orifice of thefront edge flow passage 16, convection-cools welded joints 22 of theinner shrouds, and is discharged from the rear edge 23.

The regulating plate 18 is provided to prevent reduction in flow speedof the cooling air 19 which passes through the front edge flow passage16 by narrowing the cross sectional area of the passage, and to enhancethe cooling efficiency of the front edge 15. The turbulator 20 agitatesthe cooling air 19 in the front edge flow passage 16, and enhancescooling efficiency of the front edge 15. The central flow passage 21 andthe side edge flow passage 24 have cross sectional areas smaller thanthose of the front edge flow passage 16. Therefore, flow speed of thecooling air 19 passing through the flow passages 21 and 24 is fasterthan that in the front edge flow passage 16. Thus, the structure inwhich the flow passage is narrowed enhances the cooling efficiency nearthe welded joints 22 of the inner shrouds 2 and near the side edge 25.

The cooling air 19 supplied to the cavity 12 is used as sealing air forsealing a gap (not illustrated) between the gas turbine stationary bladeand a gas turbine rotor blade. A portion of the sealing air is blown outfrom a bottom surface section of the front edge 15, to film-cool theinner shroud 2 from the front edge 15.

According to research of the present inventors, however, there has beenfound a phenomenon that corner sections of the front edge 15 of theinner shroud 2 in the conventional gas turbine stationary blade areburned 26, 26 and that thermal barrier coating (TBC) which is applied tothe surface is removed (refer to FIG. 15). It is conceived that this isbecause in the conventional technique, the flow passages 16 and 24 ofthe cooling air 19 are not in communication up to the corner section ofthe front edge 15 and that the corner section is insufficiently cooled.Further, in the conventional technique, it is conceived that since boththe flow passages of the central flow passage 21 and the side edge flowpassage 24 are pulled out from the edge flow passage 16, the flow speedof the cooling air 19 passing through the flow passages 21 and 24 isreduced to cause reduction of the cooling efficiency.

A method in which the regulating plate 18 and the turbulator 20 areprovided to maintain the cooling efficiency like the conventionaltechnique has a problem that the cooling efficiency of the cornersection of the front edge 15 is inferior and the gas turbine structureis complicated to increase production costs. A method in which the flowrate of the cooling air 19 in the inner shroud 2 is largely increased toenhance the cooling efficiency has a problem that driving cost of thegas turbine increases. There is another method in which the crosssectional areas of the central flow passage 21 and the side edge flowpassage 24 are narrowed to increase the flow speed of the cooling air19, but if the cross sectional area of the flow passage is excessivelynarrowed, the range that can be cooled is also narrowed, and thereforethe cooling efficiency of the corner section of the front edge 15 isfurther lowered.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a gas turbine stationaryblade for effectively cooling the inner shroud with a simple structure.

The gas turbine stationary blade according to this invention comprises astationary blade section provided therein with a passage for coolingair, an inner shroud for supporting the stationary blade section on theside of a discharge port of the cooling air, and a plurality of segmentseach of which includes at least one of the stationary blades and atleast one of the inner shrouds and which are coupled to one another inan annular form. At least one flow passage is pulled out from thedischarge port of the cooling air of the stationary blade section, andthe flow passage is introduced to a corner section on the side of afront edge of the inner shroud and is extended rearward along a sideedge of the inner shroud.

Other objects and features of this invention will become apparent fromthe following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B show plan sectional views which show inner shroud ofan embodiment of the present invention,

FIG. 2 is a plan sectional view which shows a meandering flow passage ofcooling air,

FIG. 3 is a plan sectional view which shows a widened flow passage ofcooling air,

FIG. 4 is a perspective view which shows a front edge acute angle cornersection provided with film cooling holes,

FIG. 5 is a perspective view which shows a front edge obtuse anglecorner section provided with film cooling holes,

FIG. 6 is a perspective view which shows front edge corner sectionsprovided with a covering member,

FIG. 7 is a perspective view which shows front edge corner sections eachhaving a rounded corner section,

FIG. 8 is a perspective view which shows side edges each having achamfered end,

FIG. 9 is a perspective view which shows bolt jointing faces providedwith a face plate to be assembled,

FIG. 10 is a front sectional view of FIG. 9,

FIG. 11 is a perspective view which shows bolt jointing faces providedwith a projected face plate to be assembled,

FIG. 12 is a front sectional view of FIG. 11,

FIG. 13 is a perspective view which shows shiplap type bolt jointingfaces,

FIG. 14 is a perspective view which shows blade series of the gasturbine stationary blade,

FIG. 15 is a perspective view which shows the inner shroud and itsperiphery of the gas turbine stationary blade,

FIG. 16 is a plan sectional view of the conventional inner shroud,

FIG. 17 is a sectional view taken along the line I—I in FIG. 16, and

FIG. 18 is a sectional view taken along the line II—II in FIG. 16.

DETAILED DESCRIPTIONS

Embodiment of this invention will be described in detail below withreference to the drawings. However, this invention is not limited by theembodiment. Any elements that can usually be changed by a person skilledin the art are included in constituent elements described in thefollowing embodiment.

According to the research of the present inventors, the burnout 26occurs if the combustion gas 6 is trapped into the gap 7 of the innershrouds 2 when the gas turbine is driven and the thermal barriercoatings of the corner sections 30 and 32 of the front edge 15 aresubjected to corrosion. In this invention, in order to prevent theburnout 26, the corner section of the front edge 15 of the inner shroud2 is provided with a cooling structure, or trapping itself of thecombustion gas 6 is restrained.

FIG. 1A and FIG. 1B show sectional plan views which show an inner shroudof a segment constituting a gas turbine stationary blade according tothe embodiment of this invention, in which FIG. 1A shows one embodimentand FIG. 1B shows another embodiment. In the figures, the sameconstituent elements as those in the conventional gas turbine stationaryblade are designated with the same numerals, and explanation thereof isomitted.

In FIG. 1A, a unit of the inner shroud 2 on the side of an obtuse anglecorner section 30 (right side as viewed from a flow-in direction of thecombustion gas 6) includes an open chamber 11 which is in communicationwith a front edge passage 9 of the stationary blade section. One flowpassage 31 of cooling air 19 is pulled out in a direction of the frontedge 15 of the inner shroud 2 from the open chamber 11. This flowpassage 31 on the side of the obtuse angle corner section 30 (“obtuseangle corner section flow passage 31”, hereinafter) has a rectangularcross-section substantially uniformly.

The obtuse angle corner section flow passage 31 is bent at two sectionslike a hook as shown in FIG. 1A. Its first bend 31 a is located near amiddle portion of the front edge 15. A middle straight section 31 b ofthe obtuse angle corner section flow passage 31 extends along the frontedge 15, and its second bend 31 c is located in the obtuse angle cornersection 30. A final straight section 31 d of the obtuse angle cornersection flow passage 31 extends rearward from the obtuse angle cornersection 30 along the side edge 25, and comes out from the rear edge 23.

A unit of the inner shroud 2 on the side of an acute angle cornersection 32 (left side as viewed from the flow-in direction of thecombustion gas 6) comprises the open chamber 11 and one flow passage 33of cooling air 19 like the unit on the side of the obtuse angle cornersection 30. The flow passage 33 on the side of the acute angle cornersection 32 (“acute angle corner section flow passage 33”, hereinafter)is installed in the same manner as that of the obtuse angle cornersection flow passage 31 except that the flow passage 33 is bent at twosections like a hook as shown in FIG. 1A.

Washers are provided on outsides of the inner shrouds 2 of respectiveunits forming the welded joints 22 for the unit on the side of theobtuse angle corner section 30 and the unit on the side of the acuteangle corner section 32, and these units are fastened and fixed to eachother by bolts and nuts (not illustrated). A pair of unit bodiesprepared in such a manner is mounted to the segment for support underpressure.

When the gas turbine is actuated, a cooling air 19 is sent from theouter shroud 4 to the open chamber 11 through the stationary bladesection 3, and flows into each of the flow passages 31, 33 pulled outfrom the open chamber 11 in a direction of the front edge 15. Thecooling air 19 convection-cools a shoulder port of the front edge 15, acorner of the front edge 15, and the side edge 25, and is dischargedfrom the rear edge 23. FIG. 1B shows another embodiment in which coolingpassages 21, 21 are provided also on the side of a bolt/nut joint faceof the inner shroud 2.

Although a shape of the cross-section of the respective flow passages31, 33 is rectangular in this embodiment, the shape is not limited tothis example, and may be circular or triangular. As the cross sectionalarea of the respective flow passages 31, 33 is smaller, flow speed ofthe cooling air passing through the passage is increased, which enhancesthe cooling efficiency. However, if the cross sectional area of the flowpassage is excessively small, a range to be cooled by the cooling airbecomes narrow. Therefore, it is preferable to appropriately change thecross sectional area of the respective flow passages 31, 33 inaccordance with a specification or the like of the gas turbine.

In the embodiment, although the obtuse angle corner section flow passage31 is of the above described hook shape, the shape is not limited tothis, and may be of a ticking symbol or the hook shape more widelyopened at an end of the shorter passage. This is because a burnout 26 ofthe inner shroud 2 can be prevented only if the obtuse angle cornersection flow passage 31 passes through the corner section of the frontedge 15 and the side edge 25 of the inner shroud 2. The same can be alsoapplied to the acute angle corner section flow passage 33.

The acute angle corner section flow passage 33 may meander at the acuteangle corner section 32 where the burnout 26 is remarkable (refer toFIG. 2). In this structure, the cooling air 19 meanders in the acuteangle corner section 32 of the inner shroud 2 through the flow passage33. The cooling air 19 convection-cools the acute angle corner section32, and passes through the side edge flow passage 24 to be dischargedfrom the rear edge 23. According to this structure, since the number ofthe flow passage 33 of the cooling air 19 is one, the flow speed of thecooling air 19 is not lowered so much even if the burnout 26 includes arelatively wide range. According to this structure, the meandering flowpassage 34 is possible to effectively cool the acute angle cornersection 32 having remarkable burnout 26.

When the acute angle corner section flow passage 33 passes through theacute angle corner section 32, its flow passage width may be widened tosubstantially the same width as a range of the burnout 26 to obtain aflow passage 35, and the regulating plate 18 may be installed on itsfloor section. In this structure, the regulating plate 18 functions tomaintain the cross sectional area of the acute angle corner section flowpassage 33 to be substantially constant. Therefore, the cooling air 19passes through the widened flow passage 35 without reducing the flowspeed, and convection-cools the acute angle corner section 32. Accordingto this structure, since the widened flow passage 35 can cool a widerange, it is possible to effectively cool the acute angle corner section32 having remarkable burnout 26.

In the above structure, turbulators 20 may further be installed on thewidened flow passage 35 (refer to FIG. 3). In this structure, theturbulators 20 agitate the cooling air 19 passing through the acuteangle corner section flow passage 33, which enhances the coolingefficiency in its installation range. According to this structure, it ispossible to further enhance the cooling efficiency of the acute anglecorner section 32.

In this embodiment, film cooling holes 36 being pulled out from theacute angle corner section flow passage 33 and having blowoff holes(refer to FIG. 4) in the acute angle corner section 32 may be provided.In this structure, a portion of the cooling air passing through theacute angle corner section flow passage 33 is discharged from the filmcooling holes to form a thin film of the cooling air 19 on the acuteangle corner section 32 of the inner shroud 2. The thin film of thecooling air 19 restrains flow-in of heat of the combustion gas 6 towardthe inner shroud 2. According to this structure, since the cooling air19 cools the acute angle corner section 32 of the inner shroud 2 fromboth sides its inside and its surface, it is possible to cool the acuteangle corner section 32 more efficiently as compared with the case wherethe film cooling holes 36 are not provided.

Especially in this embodiment, the acute angle corner section flowpassage 33 is pulled out from the open chamber 11 by the flow passage,and is not provided with a branch. Therefore, even if some fine filmcooling holes 36 are provided, the flow speed of the cooling air 19 isnot lowered so much, and it is possible to sufficiently cool the sideedge 25 of the inner shroud 2 located in a downstream region of thecooling holes. In recent years, it is possible to make the fine filmcooling holes 36 easily at a high speed by YAG laser with low cost.

It is preferable to provide the film cooling holes at a location wherethe burnout 26 of the acute angle corner section 32 of the inner shroud2 can effectively be prevented. Therefore, it is preferable that thelocation is appropriately changed in accordance with a range of theburnout 26 of the inner shroud 2 and characteristics of the flow passageof the combustion gas 6. For example, when the film cooling holes 36 arewidely provided over the entire range where the burnout 26 occurs(referto FIG. 4), it is possible to effectively cool the burnout portion 26 bytranspiration cooling effect (spill-out cooling effect).

The cooling structure of the acute angle corner section 32 of the innershroud 2 can be provided in the obtuse angle corner section 30similarly. For example, the obtuse angle corner section 30 is providedwith the film cooling holes 36 (refer to FIG. 5). Its specific structureis preferably changed appropriately within a range of knowledge of aperson skilled in the art.

In the present embodiment, a covering member 37 may be provided betweenan end of the side face of the front edge 15 of the inner shroud 2 andan end of the side face of the front edge 15 of an adjacent inner shroud2 (refer to FIG. 6). Here, the covering member 37 is a rectangular platemember 37 made of a metal material, its height is substantially the sameas that of the side face of the front edge 15 of the inner shroud 2. Inthis structure, the covering member 37 covers a gap 7 a produced betweenthe bolt jointing faces of the inner shroud 2, which prevents thecombustion gas 6 from trapping into the gap 7 a. According to thisstructure, it is possible to prevent the corner section of the frontedge 15 from being eroded by the combustion gas 6, which makes itpossible to restrain the burnout 26 of the corner section of the frontedge 15.

The shape of the covering member 37 is not limited to the abovedescribed rectangular, and may be a plate member having an L-shapedcross section (not illustrated). If the covering member 37 is formedinto such a shape, a portion up to the gap 7 a around which the burnout26 occurs can be covered with the covering member 37, and therefore itis possible to restrain the burnout 26 more effectively. The crosssection of the covering member 37 may be formed into a T-shape includinga projection having substantially the same width and height as those ofthe gap 7 a produced between the jointing faces (not illustrated). Byinstalling the covering member 37 with the projection inserted into thegap 7 a from the side face of the front edge 15 of the inner shroud 2,it is possible to fill the gap 7 a with the projection up to a portionwhere the burnout 26 occurs.

In this embodiment, a corner section of the front edge 15 of the innershroud 2 may be rounded to provide a rounded form 38 thereto, and thecorner section of the front edge 15 may be subjected to thermal barriercoating (refer to FIG. 7). A method of the thermal barrier coatingincludes known methods as follows, that is, a method of subjecting thecorner section to plasma-coating with a partially stabilized Zr 203which is a heat insulator, and a method of subjecting the corner sectionto thermal barrier coating with zirconia. In this structure, the cornersection of the front edge 15 which is provided with the rounded form 38and is smoothened moderates collision of the combustion gas 6 againstthe corner section of the front edge 15. According to this structure, itis possible to restrain the removal of the heat insulation coat on thecorner section of the front edge 15 which is erosion-prone by thecombustion gas 6, and therefore the burnout 26 can effectively berestrained. The rounded form 38 for the corner section of the front edge15 may be a chamfer formed by simply cutting the corner section off (notillustrated).

In this embodiment, an end of the side edge 25 of the inner shroud 2 mayfurther be formed with a chamfer 39, and the end of this side edge 25may be subjected to the thermal barrier coating (refer to FIG. 8). Inthis structure, the chamfer 39 on the end of the side edge 25 restrainserosion of the end of the side edge 25 by the combustion gas 6 trappedinto the gap 7 a of the inner shroud 2. According to this structure,since the removal of the thermal barrier coating on the end of the sideedge 25 is prevented, the burnout 26 is restrained.

In this embodiment, grooves 40 and 40 may be formed in bolt joint facesof adjacent inner shrouds 2 from the front edges 15 to the rear edges23, and a rectangular face plate 41 may be fitted into the grooves 40and 40 (refer to FIG. 9 and FIG. 10). In this structure, the face plate41 seals the gap 7 a between the bolt jointing faces of the innershrouds 2, and blocks the flow passage of the combustion gas 6 passingthrough the gap 7 a toward the back face of the inner shrouds 2.According to this structure, since the flow passage of the combustiongas 6 in the gap 7 a is sealed, trapping of the combustion gas 6 to thegap 7 a is restrained. Therefore, especially the burnout 26 of the sideedge end section of the inner shroud 2 is restrained. This face plate 41may not be a plate-like body and may be a columnar body (notillustrated). It is unnecessary that this face plate 41 has a lengthcorresponding to that from the front edge 15 to the rear edge 23 of theinner shroud 2, and the length may be in such a depth that the burnout26 can be recognized from the front edge 15.

A central portion of the face plate 41 may be formed with a projection42 for filling the gap 7 of the segment 1 over its length direction, andthe projection 42 may be directed to surfaces of the inner shrouds 2(refer to FIG. 11 and FIG. 12). In this structure, the projection 42 issandwiched between the jointing faces of the inner shrouds 2 to fill thegap 7. According to this structure, since the surfaces of the innershrouds 2 are flattened by this projection 42, it is possible torestrain trapping of the combustion gas 6 into the gap 7 moreeffectively as compared with the case where the projection 42 is notprovided.

In this embodiment, bolt jointing faces 43 and 43 of the inner shrouds 2may be of shiplap structure in which they are meshed with each other(refer to FIG. 13). In this structure, the stepped bolt jointing faces43 and 43 block a flow of the combustion gas 6 flowing from the frontedge 15 to the rear edge 23 through the gap 7 of the inner shrouds 2 inthe step section. According to this structure, since the flow passage ofthe combustion gas 6 passing through the gap 7 is blocked, trapping ofthe combustion gas 6 to the gap 7 is restrained. Therefore, especially aburnout 26 around the corner section of the front edge 15 of the innershroud 2 is effectively prevented. The meshed bolt jointing faces 43 and43 may not be of step-shape. For example, the bolt jointing faces may beof serrate or corrugated form.

As described above, according to the gas turbine stationary blade ofthis invention, the flow passage of the cooling air passes through thecorner section of the inner shroud. Thus, the cooling air cools thecorner section, and restrains the burnout. One flow passage of thecooling air is provided in a range from its portion pulled out from thedischarge port of the stationary blade section to its portion at leastpassing through the front edge corner section of the inner shroud.

Moreover, the inner shrouds of the segment are coupled to each other bya bolt, and therefore it is easy to disperse distortion caused bythermal stress as compared with the case where the inner shrouds areintegrally formed by welding or the like. Therefore, a local collectivestress produced particularly in an end of the stationary blade sectionor the inner shroud is relaxed, and occurrence of crack is restrained.

Furthermore, the flow passage meanders in the front edge corner sectionof the inner shroud. Therefore, even if the burnout has a quite largewidth, it is possible to effectively cool the flow passage.

Moreover, the flow passage is widened in the front edge corner sectionof the inner shroud, and therefore it is possible to cool the front edgecorner section more effectively as compared with the case where the flowpassage is not widened. Further, the regulating plate is installed onthe floor section of the widened flow passage. Therefore, the flow speedis not significantly lowered by widening the flow passage.

Furthermore, the cooling air which is flowed into the widened flowpassage is agitated by the turbulator, and therefore it is possible toefficiently cool the front edge corner section of the inner shroud.

Moreover, since the cooling air which is flowed into the widened flowpassage collides against the acicular fin and is agitated, it ispossible to efficiently cool the front edge corner section of the innershroud. Further, heat exchange is carried out between the cooling airand the front edge corner section of the inner shroud through theacicular fin and thus, it is possible to cool the corner section of theinner shroud more efficiently as compared with the case in which theacicular fin is not provided.

Furthermore, the cooling air injected from the film cooling holesfilm-cools the corner section of the inner shroud from its surface.Therefore, it is possible to cool the corner section efficientlytogether with the cooling of the inner shroud from its inside. Further,since the number of flow passage for the cooling air is one, it ispossible to cool the downstream side edge of the inner shroud whilemaintaining the relatively high flow speed even if fine film coolingholes are provided.

Moreover, since trapping of the combustion gas into the gap of the innershrouds can be prevented, it is possible to restrain the burnout of thefront edge corner section effectively.

Furthermore, since the chamfer on the front edge corner sectionrestrains removal of the thermal barrier coating, it is possible torestrain the burnout of the front edge corner section effectively.

Moreover, since the chamfer on the side edge corner section restrainsthe removal of the thermal barrier coating, it is possible to restrainthe burnout of the side edge end section effectively.

Furthermore, since the sealing member provided between the jointingfaces of the inner shrouds seals the gap between the jointing faces, andblocks the flow passage of the combustion gas coming out from the gap,trapping of the combustion gas into the gap is restrained. Therefore, itis possible to restrain burnout of mainly the side edge end section ofthe inner shroud.

Moreover, since the projection of the sealing member fills the gapproduced between the segments and flattens a surface of the innershrouds, it is possible to restrain the trapping of the combustion gasinto the gap more effectively as compared with the case where theprojection is not provided.

Furthermore, since the jointing faces of the shiplap type formed on theinner shrouds seal the flow passage of the combustion gas passingthrough the gap between the inner shrouds, trapping of the combustiongas into the gap is restrained, and particularly the burnout in thefront edge corner section of the inner shroud is effectively prevented.

Although the invention has been described with respect to a specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

1. A gas turbine stationary blade comprising: a stationary blade sectionprovided therein with a passage for cooling air; an inner shroud forsupporting the stationary blade section on the side of a discharge portof the cooling air; and a plurality of segments each of which includesat least one of the stationary blades and at least one of the innershrouds, and which are coupled to one another in an annular form,wherein the segments are assembled in such a manner that a side end faceof the inner shroud is connected to that of another inner shroud of anadjacent segment by using a bolt joint, wherein at least one flowpassage is pulled out from the discharge port of the cooling air of thestationary blade section, and the flow passage is introduced to a cornersection on the side of a front edge of the inner shroud and is extendedrearward along a side edge of the inner shroud.
 2. The gas turbinestationary blade according to claim 1, wherein the flow passage meandersin a front edge corner section of the inner shroud.
 3. The gas turbinestationary blade according to claim 1, wherein the flow passage inwidened in a front edge corner section of the inner shroud, and whereina turbulator is installed on the floor section or a ceiling section ofthe widened flow passage.
 4. The gas turbine stationary blade accordingto claim 1, wherein the flow passage is widened in a front edge cornersection of the inner shroud, and wherein an acicular fin is formed fromthe floor section to the ceiling section of the widened flow passage. 5.The gas turbine stationary blade according to claim 1, wherein filmcooling holes are formed by being pulled out from the flow passage andare provided on a front edge corner section of the inner shroud.
 6. Agas turbine stationary blade assembly comprising: a plurality ofsegments coupled to one another in an annular form, each of saidplurality of segments including; a first inner shroud and a second innershroud fixed to each other side by side, wherein each of the first andsecond inner shrouds has a first edge and a second edge, and a firstside edge and a second side edge, the first edge being on an upstreamside and the second edge being on a downstream side with respect to gasflow, wherein the first and second inner shrouds being fixed to eachother on the first side edges thereof, with the second side edgesthereof outside, and wherein each of the first and second inner shroudshas a corner section defined by the first edge and the second side edge;a first stationary blade section and a second stationary blade section,each of which is provided therein with a passage for cooling air and hasa discharge port for the cooling air on one end, wherein the first andsecond stationary blade sections are supported by the first and secondinner shrouds, respectively, on the end of the blade section where thedischarge port is provided; wherein the segments are assembled in such amanner that a side end face of one of the inner shrouds in one segmentis connected to that of another of the inner shrouds in an adjacentsegment by using a bolt joint; and wherein each of the first and secondinner shrouds is provided therein with a flow passage that communicateswith the discharge port and extends in the corner section and along thesecond side edge toward the second edge.
 7. The gas turbine stationaryblade according to claim 6, wherein the flow passage has a meanderingportion in the corner section.
 8. The gas turbine stationary bladeaccording to claim 6, wherein the flow of passage widened in a frontedge corner section of the inner shroud, and wherein a turbulator isinstalled on the floor section or a ceiling section of the widened flowpassage.
 9. The gas turbine stationary blade according to claim 6,wherein the flow of passage widened in a front edge corner section ofthe inner shroud, and wherein an acicular fin is formed from the floorsection to the ceiling section of the widened flow passage.
 10. The gasturbine stationary blade according to claim 6, wherein the cornersection of the inner shroud is provided with film cooling holes thatcommunicate with the flow passage.
 11. The gas turbine stationary bladeaccording to claim 6, wherein each of the first and second inner shroudsis provided therein with another flow passage that communicates with thepassage for cooling gas and extends along the first side edge.